SANAA (Reuters) – Yemen’s opposition warned the government on Thursday that violence against street protesters demanding the removal of President Ali Abdullah Saleh could derail a deal aimed at ending the political standoff.

Plainclothes gunmen killed 12 people and wounded dozens more in Yemen’s capital on Wednesday when they opened fire on anti-government marchers just days before a Gulf-mediated deal to end the crisis was due to be sealed. “In the event of your inability to protect protesters, we will find ourselves unable to pursue an agreement that the regime seeks to use to shed more blood,” the opposition coalition said in a statement.

A deal to end the crisis by easing Saleh out within a month was expected to be signed on Sunday in Riyadh, three months after Yemenis took to the streets, inspired by revolts that toppled autocratic rulers in Egypt and Tunisia.

But on Thursday Saleh appeared to raise a potential problem when he told Russia’s Arabic language Russia Today channel that he objected to the presence of Qatari representatives.

“We will have reservations about signing if representatives of Qatar are present among the Gulf foreign ministers,” Saleh said. “(Qatar) is involved in a conspiracy not just against Yemen but against all Arab countries.”

He singled out Qatar’s pan-Arab television channel Al Jazeera, which Saleh has accused in the past of provoking the protests. He also accused Qatar, a tiny but gas-rich Gulf state, of funding the opposition in Yemen.

The balance of power has tipped against Saleh, long a key ally of the West against al Qaeda, after weeks of violence, military defections and political reversals.

Wednesday’s killings capped a day of demonstrations by tens of thousands of Yemenis, many protesting against a plan supported by the government and the main opposition group which would give Saleh a month-long window to resign.

The protesters in Sanaa demanding Saleh resign immediately were shot at while attempting to reach an area beyond the district where they have been camped out since February, witnesses said. Ten died on the spot, while two more died of wounds on Thursday, doctors said.

In addition to the 12 killed in Sanaa, a protester and a soldier also died in clashes during protests in the southern port city of Aden on Wednesday.

On Thursday night armed men opened fire on state security offices in Zinjibar in south Yemen killing one soldier, and gunmen exchanged fire with guards outside the central bank in the port city of Aden.

The large turnout at protests against the Gulf deal showed the ability of the largely young protesters, from students to tribesmen to activists, to act as potential spoilers. They have vowed to stay in the streets until their demands are met.

It was also not clear that opposition parties, comprised of Islamists, Arab nationalists and leftists who have been in and out of government in past years, could halt the protests even if required to by the transition agreement.

SALEH TO SIGN DEAL ON SATURDAY

Washington and neighboring oil producer Saudi Arabia want the standoff resolved to avert a descent into more bloodshed in the Arabian Peninsula state that would offer more room for a Yemen-based al Qaeda wing to operate.

A government official said that Saleh, who has ruled for 32 years, would sign the agreement on Saturday in Sanaa, a day ahead of the official signing ceremony in the Saudi capital, which Saleh was not expected to attend.

On Sunday, the ruling party’s vice president and a former prime minister, Abdel-Karim el-Eryani, would sign in Riyadh on behalf of the party, the official said. The opposition would also sign on Sunday.

Both sides were expected to host large rallies in Sanaa on Friday ahead of the signing. The government planned a “Friday of Constitutional Legitimacy,” while the opposition planned a “Friday of Honouring Martyrs.”

The deal, brokered by the six-member Gulf Cooperation Council, would give Saleh and his family and aides immunity from prosecution.

It provides for Saleh to appoint a prime minister from the opposition, who would then form a transition government ahead of a presidential election two months after his resignation. But the one-month window for Saleh to resign has sparked fears it may offer time for potential sabotage.

Whoever leads Yemen’s transitional government will not only struggle to quash an aggressive al Qaeda branch, which has tried to hit U.S. and Saudi targets, but also inherit simmering rebellions in the north and south of the country.

Around 142 protesters have been killed as unrest has swept Yemen, where some 40 percent of its 23 million people live on $2 a day or less, and a third face chronic hunger.

The Interior Ministry said on Thursday that more than 21 policemen had died and 1,000 had been wounded since February 3.

SANAA (Reuters) – Yemenis flooded the streets of Sanaa and Taiz on Friday in rival demonstrations for and against President Ali Abdullah Saleh, who gave a guarded welcome to a Gulf Arab plan for a three-month transition of power.

He told supporters in Sanaa any arrangements had to be “within the framework of the Yemen constitution” — language which could mask objections to the plan — and also vowed to “confront challenge with challenge,” but without bloodshed.

“Guns can be used today but you cannot use them to rule tomorrow. We reject war,” Saleh declared.

Ten soldiers were killed in three attacks by tribesmen and al Qaeda militants in several provinces, officials said.

In the southern city of Taiz, riot police fired in the air to keep vast, unruly crowds of pro and anti-Saleh demonstrators apart, but there were no serious injuries, witnesses said.

A sea of anti-Saleh protesters, perhaps in the hundreds of thousands, inundated the streets of Taiz, Yemen’s third city and an epicenter of opposition to the 69-year-old president.

But in Yemen’s northwestern city of Hajja, a 12-year-old boy was shot dead when security forces opened fire to prevent a crowd of anti-government protesters entering the city, witnesses told Reuters by telephone.

Tens of thousands of Saleh loyalists turned out in Sanaa, the capital, for what they called a “Friday of Reconciliation,” waving Yemeni flags and pictures of the president.

Their numbers were matched by protesters demanding Saleh’s immediate departure, spilling out of their usual protest area around Sanaa University to mark a “Last Chance Friday” in nearby Siteen street, where there was a heavy security presence.

That raised concern that Saleh’s security forces and republican guards might clash with troops loyal to renegade general Ali Mohsen, protecting the protesters in Sanaa.

Demonstrators voiced skepticism about the latest Gulf plan aimed at halting Yemen’s descent into more violence and chaos.

The proposal of the six-nation Gulf Cooperation Council (GCC) calls for Saleh to hand power to his vice president one month after signing an agreement. He would appoint an opposition leader to lead an interim cabinet tasked with preparing for presidential elections two months later, a Yemeni official said.

IMMUNITY FROM PROSECUTION

The plan, presented on Thursday, also gives immunity from prosecution to Saleh, his family and aides — anathema to his foes, who would also have to end protests under the proposal.

“We won’t depend on any initiative that doesn’t demand that this man leaves right away,” said protester Manea Abdullah. “We are sticking to the demands of the revolution for an immediate departure and prosecution of those who killed our comrades.”

Saleh’s long-time Gulf and Western allies, concerned that chaos in Yemen will open more opportunities for ambitious al Qaeda militants, are trying to broker an orderly transition after three months of protests against Saleh’s 32-year rule.

Protests in the southern port of Aden started up later in the evening on Friday, as thousands of demonstrators calling for Saleh’s departure sought to avoid temperatures of over 40 degrees celsius (104 degrees Fahrenheit).

While organized opposition parties may still be ready to do a deal, many protesters do not trust Saleh to implement it.

“This guy is a liar, we won’t believe anything even if the opposition accepts the Gulf initiative,” said Abdulnasser Ahmed.

“Every time he agrees to something, then backs off. We know his ways and so does the rest of the world. That’s why the world should support our demands that he go.”

In the lawless eastern province of Maarib, a local official said anti-Saleh tribesmen had ambushed troops trying to secure a key route for gas shipments, killing two soldiers, wounding 18 and destroying a tank and an armored vehicle.

Tribesmen disrupting the main road from Sanaa to Maarib, where most of Yemen’s gas is produced, have made it impossible for trucks to distribute cooking gas to the rest of the country.

Shortages have quadrupled cooking gas prices on the black market to 5,000 rials ($20) from 1,200. Infuriated residents have blocked roads in some Sanaa districts with empty gas bottles. The crisis has prompted others to join anti-Saleh protests, where they have scrawled “Leave” on gas canisters.

Prolonged turmoil has driven the rial to near-record lows of around 250 to the dollar from 214 nine weeks ago. It has become harder to find outlets ready to sell dollars, residents say.

Violence involving suspected al Qaeda militants also flared on Friday, with seven soldiers killed when their convoy came under fire in Maarib, a government official said.

One soldier was killed and another wounded when the army clashed with gunmen thought to belong to al Qaeda’s Yemen-based wing tried to seize a post office in Zinjibar, in the southeastern province of Abyan. The armed men later sped away on motorcycles.

The toll in a Thursday night clash in the southern province of Lahej rose to five soldiers killed and three wounded, according to a local official. Two militants were also killed.

(Additional reporting by Mohammed Mukhashaf in Aden and Erika Solomon in Dubai; writing by Alistair Lyon; editing by Philippa Fletcher)